<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>bootstrap</title>
    <link rel="stylesheet" href="css/bootstrap.min.css">
    <style>
    .fz div {
        font-size: 50px;
    }
    </style>
</head>
<body>
<div class="container">
    <div class="row fz text-center">  <!-- 行 -->
        <div class="col-lg-6">1</div>
        <div class="col-lg-6">2</div>
    </div>
</div>

<div class="container">
    <div class="row fz text-center">  <!-- 行 -->
        <div class="col-lg-3 col-sm-6 col-xs-12">A</div>
        <div class="col-lg-3 col-sm-6 col-xs-12">B</div>
        <div class="col-lg-3 col-sm-6 col-xs-12">C</div>
        <div class="col-lg-3 col-sm-6 col-xs-12">D</div>
    </div>
</div>

</body>
</html>